The gloss of a printing medium printed by an image output apparatus such as a color printer or the like is an important image quality factor in the field of photo printing and document printing, and is used as one of quality management items of printing media. The printing media have different gloss states of their surfaces depending on print methods, color materials, paper sheets, and the like.
An evaluation method of the gloss of a printing medium generally uses a measured value of a glossiness meter compliant with a specular glossiness measurement method (JIS Z 8741) that measures the intensity of specular reflected light. Glossiness evaluation of a highly gloss object such as the outer panels of an automobile uses a measured value of haze meter compliant with reflection hase measurement method (ISO 13803, ASTM E 430) for measuring the tarnish degree of a sample surface, and an image clarity measurement method (JIS K 7105, JIS H 8686) for measuring the distinctness of image that appears on a sample surface.
While printing with electro-photographic printer uses pigment toner and pigment ink inkjet printers, color materials remain on the surface of media other than infiltrating the printing medium. Therefore, the surface structure and color material, which have different refractive index from media, exposure ratio of printings vary according to colors and densities that cause gloss nonuniformity.
As a method of evaluating the gloss of an object in such an environment, for example, patent reference 1 is known. This patent reference 1 uses, as a gloss evaluation value, a linear sum of a gloss index value obtained based on specular reflected light and an index value associated with lightness obtained based on diffused reflected light.
Patent reference 1: Japanese Patent Laid-Open No. 2004-317131